Carpenters' squares are well known in the art. The conventional square tool is simply an L-shaped piece of flat metal having an angular juncture of 90 degrees. A square of this type is shown in U.S. Pat. No. 3,623,232. Similar squares are shown in U.S. Pat. Nos. 4,573,276 and 513,665. Other relevant marking guides and guages are shown in U.S. Pat. Nos. 3,395,456; 2,965,696; 3,010,209; and 1,732,906.
While the varieties of squares and similar devices shown in the patents referred to above are apparently well suited for their intended purposes, until the present invention there has been no specific tool for use in squaring and marking a notch in the end of a floor joist to allow for placement thereof upon a ledger and for use in marking the intended position of a ledger on a girder. It is for this reason that the present floor square was invented.